Upstream Paper

src/main/java/org/bukkit/craftbukkit/entity/CraftVex.java

@@ -38,4 +38,14 @@ public class CraftVex extends CraftMonster implements Vex {
     public EntityType getType() {
         return EntityType.VEX;
     }
+
+    @Override
+    public boolean isCharging() {
+        return getHandle().dA();
+    }
+
+    @Override
+    public void setCharging(boolean charging) {
+        getHandle().a(charging);
+    }
 }

src/main/java/org/bukkit/craftbukkit/inventory/InventoryWrapper.java

@@ -128,7 +128,7 @@ public class InventoryWrapper implements IInventory {
         List<ItemStack> items = new ArrayList<ItemStack>(size);
 
         for (int i = 0; i < size; i++) {
-            items.set(i, getItem(i));
+            items.add(getItem(i));
         }
 
         return items;